1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor wafer, in particular, to a method for mirror-finishing the beveled surfaces located at the peripheral rims of semiconductor wafers.
2. Description of the Related Art
Conventionally, beveling of the peripheral rims of semiconductor wafers has been performed for the purpose of avoiding chipping or breakage during the process of polishing or flattening such as lapping. Recently, high flatness of the beveled peripheral portions is required so as to enhance the yield during device processing. Therefore, it is necessary to finish them by mirror-polishing. The mirror-polishing of the peripheral portions of the semiconductor wafers has been performed by using a polishing unit as follows: A beveling device, in which a grinding wheel is installed, shapes the beveled portions of semiconductor wafers. Then, a polishing unit, whose surface is provided with a polishing pad affixed thereon, is guided to urge against the beveled portions of the semiconductor wafer to be polished. Afterward, mirror-polishing is performed by supplying slurry.
However, to accurately polishing the beveled portions with the aid of the polishing unit, it is essential to analyze the slanted angle of the beveled portion and control the polishing unit based on the analyzed data.
Furthermore, to polish the beveled portion into the shape of a taper, three surfaces have to be polished. Those are thr front-side tapered surface, the outer peripheral surface, and the rear-side tapered surface. The three surfaces have to be polished by separate polishing units and the wafer has to be turned over, therefore processing time is long.
In addition, the boundary portions among the front-side tapered surface, the outer peripheral surface, and the rear-side tapered surface are quite difficult to be mirror-polished. Therefore, there exists a possibility that the boundary portions will remain not mirror-polished.